wasm: fix redundant string conversions between wasm and JavaScript

Avoid redundant conversions from UTF16 to UTF8 to UTF16 with
help of new class QWasmString static methods:
+ QWasmString::fromQString to convert QString to js string
using js Module.UTF16ToString
+ QWasmString::toQString to convert js string to QString
using js Module.stringToUTF16

Fixed document.getElementById calls for cavasId with unicode characters.

Change-Id: I3fc55bfeb6aeda75fa3acd85d22cea667b542f38
Reviewed-by: Morten Johan Sørvig <morten.sorvig@qt.io>
Reviewed-by: Lorn Potter <lorn.potter@gmail.com>

1 files changed, 6 insertions, 5 deletions

diff --git a/src/plugins/platforms/wasm/qwasmintegration.cpp b/src/plugins/platforms/wasm/qwasmintegration.cpp
index 1e9f68027c..fd53cd0bae 100644
--- a/src/plugins/platforms/wasm/qwasmintegration.cpp
+++ b/src/plugins/platforms/wasm/qwasmintegration.cpp
@@ -36,6 +36,7 @@
 #include "qwasmclipboard.h"
 #include "qwasmservices.h"
 #include "qwasmoffscreensurface.h"
+#include "qwasmstring.h"
 
 #include "qwasmwindow.h"
 #ifndef QT_NO_OPENGL
@@ -67,19 +68,19 @@ static void browserBeforeUnload(emscripten::val)
 
 static void addCanvasElement(emscripten::val canvas)
 {
-    QString canvasId = QString::fromStdString(canvas["id"].as<std::string>());
+    QString canvasId = QWasmString::toQString(canvas["id"]);
     QWasmIntegration::get()->addScreen(canvasId);
 }
 
 static void removeCanvasElement(emscripten::val canvas)
 {
-    QString canvasId = QString::fromStdString(canvas["id"].as<std::string>());
+    QString canvasId = QWasmString::toQString(canvas["id"]);
     QWasmIntegration::get()->removeScreen(canvasId);
 }
 
 static void resizeCanvasElement(emscripten::val canvas)
 {
-    QString canvasId = QString::fromStdString(canvas["id"].as<std::string>());
+    QString canvasId = QWasmString::toQString(canvas["id"]);
     QWasmIntegration::get()->resizeScreen(canvasId);
 }
 
@@ -115,11 +116,11 @@ QWasmIntegration::QWasmIntegration()
         int screenCount = qtCanvaseElements["length"].as<int>();
         for (int i = 0; i < screenCount; ++i) {
             emscripten::val canvas = qtCanvaseElements[i].as<emscripten::val>();
-            QString canvasId = QString::fromStdString(canvas["id"].as<std::string>());
+            QString canvasId = QWasmString::toQString(canvas["id"]);
             addScreen(canvasId);
         }
     } else if (!canvas.isUndefined()){
-        QString canvasId = QString::fromStdString(canvas["id"].as<std::string>());
+        QString canvasId = QWasmString::toQString(canvas["id"]);
         addScreen(canvasId);
     }